The present invention relates in general to seismic sensors and, more particularly, to a method and apparatus for planting the seismic sensors in the ground in a vertical orientation.
Present methods of seismic data acquisition require surveying a field prior to installation of seismic receivers. The user surveys the field in order to determine the precise location for each of the seismic receivers. A field surveying crew selects positions for each of the seismic receivers. An installer manually plants the seismic receivers according to the locations determined by the crew. The installer must plant each of the seismic receivers in the ground in near vertical position. Failure to plant the seismic receivers in near vertical position results in faulty readings. Thus, a great deal of time and effort are expended in surveying the field and ensuring near vertical planting.
Other known methods of surveying include locating the receivers in relation to known coordinates, such as the location of an acquisition box. The location of the acquisition box is determined with a survey receiver at a relatively high cost. Once the location of the acquisition box is known, the installer measures a certain distance in a specific direction and plants the seismic receiver. Consequently, the actual location of each seismic receiver is inferred based on spatial relation to the acquisition box's location, which reduces accuracy.
Current methods require the installer to stoop down in order to plant the seismic receivers. This increases work time and costs, while reducing accuracy, because vertical alignment is difficult to determine until testing the adequacy of the vertical plant. If testing shows that the seismic receivers are not vertical, then the installer must spend more time replanting and repositioning the seismic receivers until the seismic receivers are in near vertical alignment.
Once the installation is complete, the installer runs remote tests to verify that the receivers are vertically aligned within a certain tolerance. The remote tests involve using a pulse to determine if the receiver has proper vertical alignment. The pulse moves the geophone element and the response is checked for free movement. These remote tests indicate only that a problem exists. These tests do not indicate the cause of the problem or the location of the seismic receiver causing the problem.
In addition to vertical alignment, the seismic receivers must also be planted firmly in the ground to ensure adequate coupling of the seismic energy to the seismic receivers. It is difficult for an installer to firmly plant the seismic receiver. The installer can not determine the adequacy of the coupling using known methods. The installer can not wiggle or rock the seismic receiver to determine if it has been firmly planted because wiggling or rocking the seismic receiver wallows out the surrounding ground. Wallowing causes gaps between the ground and the seismic receiver resulting in poor coupling between the ground and the receiver, which causes inaccuracy in measuring due to attenuation of the seismic energy.
Furthermore, known methods utilize a multi-channel acquisition unit to collect and transfer data collected by each of the geophones. The geophones are connected using multiple wires, which increases cost and labor effort for deployment. Additionally, the interconnecting wires can be easily damaged. If a wire is damaged the user is informed that there is a problem with the receiver. However, when a problem with the receiver is indicated, without field testing and inspection, the user can not determine whether the problem is caused by a damaged wire or a problematic geophone. Accordingly, more time and money must be spent to distinguish between errors due to the damaged wire or the problematic geophone.
Therefore, what is needed is an apparatus and a method for planting seismic receivers for both good coupling to the ground for data acquisition, and vertical planting, while substantially eliminating the need for interconnecting wires and costly surveys.